Oven



S. TROOD.

OVEN,

APPLICATION FILED SEPT.24, 1920.

Patented Oct. 11, 1921.

3 SHEETS-SHEET l.

m w Y N. um. n.. .u N N N NN n S. TRGOD.

OVEN.

APPLICATION FILED SEPT.

Patented Oct. 11, 1921.

3 SHEETS-SHEET 2,

,M @qm www uw. @O

www

S. TROOD,

OVENy APPLICATION FILED sEPT.24, 1920.

Patented Oct. 11, 1921.

3 SHEETS-SHEET 3.

UlNlTED SAMUEL TIROGID, F 'ETTSBURG-I, PENNSYLVANIA.

QVJEN.

To all whom may concern heating chamber 2. The goods or articles,

Be it known that I, SAMUEL Tnoon, a citizen of the United States, residing` at Pittsburgh, in the county of Allegheny and State of ennsylvania, have 'invented a new and useful Improvement in Ovens, of which the following is a full, clear, and exact description.

rlhe present invention relates tov ovens, and more especially to ovens of the so-called continuous tunnel type, in which the articles to be heated travel 'through a long tunnellike heating chamber.

The object of the invention is to secure a better regulatedl heat distribution in the oven chamber. y

Other features of the invention relate to certaincombinations and arrangements of parts hereinafter described and more particularly -Which will \be apparent to those skilled in the art from the following description.

The present invention is illustrated and described with particular reference to a continuous tunnel oven having two lines of 0ppositely moving articles traveling through the heating chamber. lt is to be understood, however,- that the invention isv not limited to itsV illustrated embodiment but may be vembodied in other oven structures.

In the drawings, which illustrate the .pre-

"ferred embodnnent of the invention, Figure 1 is a horizontal section through the-oven;

Fig. '2 is a vertical transverse section through the oven;

.Fig 3 is a detail view of the air preheating lugs;

1g. 4 1s a detail view villustrating a modifled construction of the heat shields, and .v

Figs. 5, 6 and -7 are detail views showing one of the heat flues and its conducting' plates and illustrating different ways in which the desiredl heat zones may be maintained.

Asshown in the drawings, the oven 1 is a longv structure having a long tunnel-like to bev heated travel through the oven chamber in two rows traveling 1n opposite directions. The artlcles are shown as carried ontrucks 3 which move in opposite directions on two sets of tracks 4; and 5. The trucks have metal frames upon which are carried refractory platforms or tables 6 upon which the articles to be heated are placed. The articles to be heated are illustrated as sagpointed out, the advantages of l Specication of Letters Patent. lPatented Oct. 11,1921.

Application led September 24, 1920. Serial No. 412,575.

gers inclosing ceramic Ware. shown merely for the lpurpose of illustration, as any desired articles may be heat These are treated in the oven. The trucksare provided with the usual sand seals 8 to'prevent the hot gases from getting beneath the metal bodies of the trucks. 4'lhe two rows of trucks are pushed through the furnace by means of any chamber 2. A burner 21 discharges into they combustion chamber 22 of the heating iue where combustion takes place. -The products o-f-combustion travel along the flue proper 23 to the chimneyv iue 24. An opening 25 is provided for diverting a fraction of the hot gases of combustion from the flue 23 to the mouth ofthe burner 21 to assist in elevating the temperature of the gases where combustion takes place. It will be noted that the burnerl 21 discharges into the combustion chamber22 in one direction, and that the gases turn on themselves and flow along the side of the combustion chamber next the oven and along the Hue in the opp osite direction. This enables 'me to get the desired -heat laces. The air forcombustion is preheated '1n a,U-shapedvpreheatingpipe 26 located at pipe` 28 with gas or other fuel. f

concentration at the right- The outer walls'v 30 of thefurnace are A formed of suitable refractory heat-insulat- 1 00 ing material. The gases offcombustion `are kept from contacting withithe articles to be heated by means of heat-conducting partition walls 31 between the combustion chambers and flues, and the oven chamber. Thesev walls are shown as made of corrugated `plates'for the purpose of getting more surface to transmit the heat t rough the partitions. The walls 31 aremade of a highly refractory heat-conducting material lWhere drawings, the portion 32 of the partition is made of plates of carborundum. The por tion of the wall 33 where there is less heat is shown as made of corrugated metal which conducts heat more readily than the Y carborundum but which could not be used at the highly heated portion of the Hue.

The plates which form the partition walls 31 are mounted sov that they may be built in after the oven roof and walls are completed -and so that they may be removed and re,-

placed if desired.' As shown in Fig. 2, the roof arch which is of refractory material like the walls 30, has projecting bricks 35 between which are held the upper ends of the plates forming thepartition walls. 31. These bricks are preferably made of 4some strong refractory material such as carborundum. The lower ends of the wall plates are set into recessed bricks 36. In putting in the walls, the wall plates are fitted between the roof bricks 35 and the recessed bricks 36 are brought up to inclose the lower ends of the wall plates. Then ordinary rectangular bricks 37 are thrust beneath the recessed bricks 36 to support them and to hold the wall plates locked'in position.

The oven chamber 2 has no central partition as in sometypes of double tunnel ovens. A central pier 40 extends along between the trucks but above this from side to side. At the extreme ends of the oven, shields 41 are providedto screen the incoming goods from a too quick heating b the heated outgoing goods. As shown in ig. 1,these heat Screens extend like wing Walls a short distance into the tunnel cham.- ber from each end and are formed of sheets of corrugated metal. These shields prevent direct exchange between the outgoing goods and the incoming goods and thereby prevent the incoming goods from receiving a too quick shock of heat, When the heat shields are formed of metal, as shown in Fig. l, preferably no openings are provided through the metal so that the heat exchange between the heated outgoing goods and incoming goods takes place by' the outgoing goods heating the metal wall 41 by convection currents between the wall and the outgoing goods. This induces convection currents between the heated shield and the incoming goods to cause a gradual heating thereof.

In Fig. 4 is illustrated a modification of the heat shields. As shown in Fig. 4, the heat shield is built up of a plurality of overlapping piers 42 having tortuous air openings between them. When this type of wall is used the incoming goods are shielded against direct heat radiations from the outgoing goods buta convection circulation of heated air is formed through the tortuous and restricted openings 43. l

As will be readi'ly understood by those two combustion chambers 2.2. Thereafter pier the oven is open lthe boiling point of waterand t skilled in this art from the foregoing description, the articles to be fired or heat treated are placed upon the trucks which are introduced into the ove'n Vchamber through the vestibules 11. These trucks are pushed through the oven chamber in opposite directions as' indicated by the arrows L in Fig. 1. As the goods travel through the oven, they are first heated by the heat from thev combustion of the fuel and also from the heat given up by the outgoing oppositely moving goods. The goods, as rst introduced into the oven, receive heat through the wall 31 on the one side, and from the heated outn going goods on the other side. This heat is tempered by the heat shield 41. lThe heat which the goods receive from the combustion of the fuel at this point ,is -a comparatively gentle heat through the metal wall 33 which is at the cooler end of the'heating flue 23. As thegoods pass beyond the end ofgthe heat shield 41, they come into the more highly heated portion of the chamber in which they are subjected to the directl heat from the'outgoing goods on the oneside and from the more highly heated refractory walls of the heating flue on the other side. The goods travel along until they reach the zone of maximum heat, which is between the they travel along opposite the wall of the furnace which has no heating flues. Here the goods are gradually cooled, giving up their heat to the oppositely moving lines of cool incoming goods. The goods are then pushed out of the furnaceinto the antechamber 114 where the gradual cooling of the oods may be completed if desired, before t ely are taken into the outer air.

his furnace structure allows a .proper distribution and regulation of the heat. In the heat treatment of certain articles it is desirable that the heat treatment follow a certain definite cycle. For example, in firing certain ceramic goods it is desirable that the goods be irst heated to sli htly above l* lien kept at this temperature for a substantial length of time, until thel free water 'is evaporated. After the water is driven off the temperature 115 of the goodys can be increased relatively rapidly untihfthe temperature of dehydration or calcinfing is reached.- Then the temperature should be held approximately constant until the water of crystallization is driven ofi". Then the goods may be again heated comparatively rapidly until the temperature of fusion of the bond or flux is reached. The goods should then be heldat substantially this temperature for a considerable length of time until the firing is completed.4 After this the temperature of the goods should be gradually reduced. For the most economical and rapid operation of an oven, the times between the necessary `periods of substantially constant temperature should be made as short as possible. For example, while the three periods of free water evaporation, dehydration, and fluxing i should consume substantial amounts of time, the transition periods may be comparatively short. In other words, the gradient of the curve representing the relation between the temperature and the time should be small at some portions of the curve and comparatively large at others. The desired time-temperature relation is obtained in the old style intermittent bee-hive oven by varying the rate of combustionto `approximate the desired time-temperature cycle. In continuous ovens the rate of combustion of the fuel must be maintained `substantially uniform. In the usual type of v continuous ovens, the temperature is gradually in- D creased so that the rise in temperature will not be too rapid during the `periods which require an approximately constant temperature. The temperature-time curve has had a small and substantially constant gradient 5 throughout. While such heating does not ydamage the goods, it consumes an unnecessary amount of time during the transition periods. In my oven, I maintain a substantially constant combustion of the fuel and at the same time get the desired quicker temperature cycle having the, necessary periods of approximately constant temperature and transition periods of-quicker temperature increase. I maintain such heat distribution in the oven chamber that the goods pass through Zones of approximately constant temperature and intervening zones of more'rapidly increasing temperature.

In Figs. 5, 6 and 7 I have illustrated three i 0 ways of a possibly greater number, of controlling the heat distribution to maintain the heating zone lwhen a Hue is utilized in which combustion. takes lplace at one end and the products of combustion travel longi- 5 tudinallyalong the flue with gradually decreasing temperature .It is to lbe understood, however, that the invention is not limited to this type of flue, or to the illustrated construction for ,establishing the heat .0 zones, as they are intended to be merely illustrative.

In Figs. 5, 6 and 7 the same heating flue as shown'l in Fig. l is illustrated. VvThis flue 20, as in Fig. 1, has the combustion chamber 22 and the lon'g Hue proper 23 between the combustion chamber and the chimney flue 24. The greatest heat is, of course, at

the point of combustion along the wall opposite the chamber 22. The heat of the gases gradually diminishes along the ylong flue 23. In these figures, I have. illustrated an arrangement whereby the goods travel through four'` zones indicated by reference characters A, B, C and-D. A represents a zone along which the temperature increases comparatively rapidly. B represents .a zone along which the temperature is approximately constant. C represents a second zone of increasing temperature. sents a second approximately constant temperature zone. Four zones are shown for the purposes of illustration. In actual practice there may be a greater number of zones and they mayI be differently arranged depending upon the character of the materials to be treated.

Referring first to `F ig. 5: The heat distribution is obtained by varying the thickness of the conducting partition wall 31. As shown in this figure, the partition wall comprises a metal plate extending from a to 7;, a comparatively thin carborundum plate ex- D repretending from b to b; a thickerscarborundum plate extending from b to d; a thicker carborundum plate extending fremd to d', and a still thicker carborundum plate extending from d to d2. It will be-seen, therefore,

that the heating chamber or flue 20 has a partition wall decreasing in thickness but in a definite manner.

It is desired to have the zone D, a zone of approximately uniform temperature. Therefore, opposite the combustion chamber 22 is placed the thickest carborundum plate. Where the gases have cooled` somewhat, as between d" and al, a thinner plate is put, and where the gases have cooled still more, as between d and b', a `still thinner plate is used.' rIhe heat can pass' more readily through the thinner plates so that by making the plates ofproper thickness and v .relative length, the heat transfer between the heating Hue. and the oven chamber may be made substantially uniform along. the zone D. It will be notedthat the portion of wall between d and b" is made comparatively long and of uniform thickness. This gives a zone C along which the heat transfer varies in accordance with the decrease in temperature ofI the flue gases. The zone B is formed by the thicker plate at one end,

the thinplate at the middle, and the still thinner and better heat conducting metallic plate at the otherl end so that a substantially constant temperature is maintained in the oven chamber along this Zone. The zone A vin which the temperature of the goods is increased,'is formed by a wall of uniform thickness. i

As shown in Fig. 6, similar heating zones are established by varying the corrugations of the partition wall. The greater the corrugation, the greater the heat transfer through the wall.

In Fig. 7 similar heating zones are established by constricting the area of the flue 23. These constrictions are indicated at 50 and 51. The heat exchange between a surface and thev gases passing over the surface is dependent, among other things, upon the ve-V yso locity of the gases passing over the surface, increasing rapidly with increase of such velocity. Therefore, the walls opposite the constrictions 50 and 51 will absorb more heat from the gases than would be the case if the constrictions were not present. In this way the right hand end of the heating zone D4 may have its temperature maintained substantially as great as the temperature opposite the combustion chamber at which the gases do not travel as rapidly over the surface ofthe wall 31. The illustrations in Figs. 5,6 and 7 are intended to be merely schematic and are therefore exaggerated, no attempt being made to get exact proportions.` The heat cycle for any particular furnace may be worked out and the heat distribution arranged to give the proper heating zones.

The term constant temperature zone is intended as a term of general description and not of limitation, and is intended to define those zones in which the variation of temperature is comparatively small as compared with the transition zones of marked temperature increase, and is intended to include zones in which there may be some increase of heat provided such increase is not great enough to damage the goods during the period in question, as for example, the evaporating, calcining, or fluxing periods of baking ceramics.

While I have illustrated and described the preferred embodiment of my invention, it is to be understood that the invention is not limited to its illustrated embodiment but may be otherwise embodied within the scope of the invention as defined in the following claims.

I claim: v

1. An oven comprising a comparatively long heating chamber through which travel the articles to be heated and means for maintaining along the heating chamber zones of approximately uniform temperature separated by zones of changing temperature, substantially as described.

2. An` oven comprising a comparatively long heating chamber through which. travel the articles to be heated and means for maintaining along the heating chamber zones of comparatively little temperature change separated by zones of comparatively rapid temperature change, substantially as described.V l

3. An oven comprising a comparatively long heating chamber through which travel the articles to be heated, a' longitudinal heating flue in the wall Iof the chamber, and means for maintaining along the oven chamber zones of approximately uniformtemperature separated by zones of comparatively rapid changing temperature by varying the rate of heat delivery along the flue, substantially as described.

ing chamber having two tracks along which the articles to be heated travel in opposite directions, means for heating the articles, and heat shields at the ends onlyv of the chamber between the lines of incoming and outgoing articles, substantially as described.

6. An oven comprising a comparatively long heating chamber through which the articles to be heated travel in two lines in opposite directions, means for heating the articles and means at the ends only of the chamber for shielding the incoming articles from the heat of the outgoing articles, substantially as described.

7. An oven comprisin a comparatively long heating chamber t rough which the articles to be heated travel in two lines in opposite directions, means for heating the articles, and means at the ends of the chamber for decreasing the heat transfer between the outgoing and incoming articles where their temperature difference is the greatest, substantially as described.

8. An oven comprising a heating chamber and a combustion flue or chamber in the wall of the oven arranged to cause a'return Voreddy of the gases of combustion, substantially as described.`

9. An oven comprising v-a heating chamber and a burner in the oven wall and a combustion chamber receiving the products of combustion from the burner and arranged "to reverse the direction of the stream of the gases of combustion, substantially as described.

10. An oven comprising a heating chamber, a combustion chamber or ilue in the wall of the oven, and a corrugated heat conducting partition between the heating chamber` and the combustion flue or chamber,

substantially as described.

11. An oven comprising a heating cham'- ber, a combustion chamber or flue in the wall ofthe oven and a generally flat, vertical, corrugated, heat conducting partition between the heating chamber and the combustion chamber or flue, and extending from the top to the base of the heating chamber, substantially as described.

12'. An oven comprising a heating chamber,'a combustion chamber or flue in the wall of the oven, partition plates between Aao the heating chamber and combustion chamber or flue, and meansfor removably holding the plates, substantially as described.

13. An oven comprising a heating chamber, a combustion chamber or. 'lue inthe wall of 'the oven, partition plates between the heating chamber and combustion chamber or line, means for removably holding the `plates comprising locking projections extending from the roof of the oven and a recessed locking means at the bottom of the plates, substantially as described.

14. An oven comprising a heating chamber having a refractory roof, a combustion chamber or 'iue in the side of the oven, a partition between the heating chamber and combustion chamber or flue comprising a plate of refractory material, and means for holding the partition plate comprising reractory blocks projecting from the roof of the heating chamber and means for holding the bottom of the plate, substantially as described.

15. An oven comprising a heating chamber having a refractory roof, a combustion chamber or flue in the side of the oven, a partition between the heating chamber and combustion chamberv or flue comprising a plate of refractory material, means for holding the partition plate comprising refractory blocks projecting from the roof of the oven chamber and means for holding the bottom of the plate including a recessed block itti'ng around the lower end of the plate and blocks slipped in beneath the recessed block to support it', substantially as described.

16. An oven comprising a comparatively long heating chamber through which the articles to be heated travel in opposite directions, means for maintaining along the heating chamber zones of comparatively little temperature change separated by zones of comparatively rapid temperature change and heat shields at the ends only of the chamber between the lines of incoming and outgoing articles, substantially as described.

17. An oven comprising a comparatively long heating chamber through which the articles to be heated travel in two lines in opposite directions, means for heating the articles, and substantially unbroken heat conducting shields at the ends only' of the chamber between the lines of incoming and outgoing articles, substantially as described.s

18. An oven comprising a comparatively long heating chamber through which the articles to be heated travel in two lines in opposite directions, means for heating the articles, and metal heat shields at the ends of.

SAMUEL TRooD. 

